Charles Kennedy's desire to become a statesman-like leader of the official opposition was evident in the words he used in his keynote conference address, a language expert claims.

The Lib Dem leader has replaced his "chat show persona" as a more confident, thoughtful speaker who demonstrated a new "gravitas", according to Professor John McRae.

This is the first of Kennedy's big speeches where he is coming through with the authority of a potential leader of the opposition

Prof John McRae

The lecturer in English language at the University of Nottingham came to his conclusions following a close study of Mr Kennedy's end of conference speech in Brighton on Thursday.

Prof McRae said Mr Kennedy used the same "rhythmic" style as Prime Minister Tony Blair, but delivered it in a "rather friendly Scottish accent that people relate to".

But while complementing Mr Kennedy on delivering an "authoritative, well balanced and confident speech", Prof McRae warned him not to indulge in cheap gags like taking the mickey out of John Prescott's two Jags.

'Rhythmic pattern'

He said only Mr Kennedy could "get away" with a description of the Tories as "they look faded. They sound jaded. The party of yesteryear".

Prof McRae said: "Blair couldn't get away that.

"It's in the same kind of rhythmic pattern as Blair, but it is said in that rather friendly Scottish accent that people relate to. It is a soundbite, but it is achievable.

Mr Blair's delivery has 'comic timing'

"It seems to me therefore that this is the first of Kennedy's big speeches where he is coming through with the authority of a potential leader of the opposition.

"Up until now, his party conference speeches have tended to be not as cutting edge as this. They have tended to be a wee bit woolly, a wee bit comfortable.

"And now who is he attacking? It isn't the government - it is the Conservatives. That is a step forward in the growth of Kennedy."

Tailored speech

Prof McRae said this deepening seriousness was evident during the recall of Parliament on Tuesday when, during the debate on Iraq, Mr Kennedy suggested that he was asking the questions that Tory leader Iain Duncan Smith should have been asking.

"He is not setting himself against Blair. He is setting himself in comparison and contrast with Iain Duncan Smith.

"It is personal on Duncan Smith.

"What Kennedy has done is tailored this speech to his voice and personality and the political situation of this week - that seems to me to be dead good."

A joke in the text related to Labour's "mixed messages" over Europe referred to "spin... and then, in case you missed it - back spin".

Prof McRae said: "The 'in case you missed it' is very much Charles Kennedy with a throwaway line. He is very, very good at that.

"I think that is something he has learned from his broadcasting careeer. He knows how to time a line.

"This speech is very, very well timed."

Tony's 'guys'

When Mr Kennedy says, "so, consistency on Europe, well you'd certainly never accuse the Labour Party of that", Prof McRae said: "It is very neat how he has constructed his argument and then done a punchline that is predictable.

"It's like Tony's 'guys'. He is sharing with the audience and getting the joke through."

But Prof McRae was critical of Mr Kennedy's reference to John Prescott where he said we had been spared "the exhaust emissions from his two Jags" when he "swapped them for five Mercedes instead".

"I wish he hadn't bothered coming out with that one. That is exactly the kind of cheap sniping which they all do.

"I actually think the public doesn't like that. Why is he doing that? It's because it makes the party conference feel good about itself, but it is exactly what puts people off party conference speeches.

"In relation to Mr Prescott's Jags, I think rather a lot of people would think 'lucky bugger'."

'Effective opposition'

Prof McRae said Mr Kennedy's opening words that the conference week had been "highly significant, if not seminal" had "lost a lot of people" as had his reference to the shadow cabinet, using the French "cabinet phantome".

"Banalities" was not a powerful enough word, compared with Tony Blair's use of "massive".

His claim that the Lib Dems were an "effective opposition" was, according to the professor, "an interesting choice of words".

"He does deliver it nicely. He is relaxed."

Prof McRae said Mr Kennedy's tone had changed dramatically from being a chat show king on Have I Got News For You, to a statesman with gravitas.

"He is taking himself seriously enough to be taken seriously by other people.

"Iain Duncan Smith could learn a lesson here. It has taken Kennedy about three years. He is now coming into his own."